At a recent fan screening of The Flash and Arrow crossover, Kreisberg explained, "There are things we can do, and there are things we can't. I'm a huge fan of Nightwing. But there are cities we can use, and then there's everything else. You won't be hearing Gotham or Metropolis on the show any time soon."

And no Gotham and no Metropolis means no Batman and no Superman, respectively.

As io9 points out, Kreisberg doesn't mention the characters by name, only the cities, but it doesn't make sense that the shows could use the characters, but not the cities. It stands to reason that Kreisberg's point is these DC cities and the characters in them are off-limits.

We're guessing Warner Bros. — who is DC Comics' parent company — wants to save Superman and Batman for the big screen. With Zack Snyder's Batman v Superman: Dawn of Justice set to release in 2016, the studio likely doesn't want to draw any hype away from that upcoming character depiction.

We have to admit: We get it. But that doesn't mean we're happy about it, just like Kreisberg seems disappointed he can't do anything with Nightwing.

We can all reconcile with the fact that we do get to indulge in Arrow and The Flash simultaneously. And their team-up/throw down is going to be epic. This is the first time the two characters will meet following Barry's transformation from regular boy into superhero. Things were never exactly smooth sailing for these two, but we have a good feeling things are definitely going to heat up. But, since they are heroes after all, they'll find a way to work together in the end. "Flash vs. Arrow" will air on Dec. 2 at 8:00 p.m. on The CW.